The present invention relates to a lighting device, in particular a lighting device for stage presentations and cinematography.
Lighting devices for theatrical and cinematic illumination must meet a variety of demands. In addition to being rapidly installable and removable, they should enable alternative light and colour effects to be achieved in frequent and quick succession, with various intensities. To avoid disturbing noises, in particular during filming with an original sound track, they should also operate as quietly as possible. Furthermore, they should provide the softest possible light.
The objective of the present invention is to provide a lighting device with which the preceding requirements can be fulfilledxe2x80x94that is, one that is easily and reliably manipulated and that can be used in combination with lights that are already available, such as stage spotlights, which reduces expense. This objective is achieved with the present invention.
The central point of the present invention is to provide a spotlight or similar lighting object with an inflatable sack through which the light passes outward, such that the emerging light is extremely soft and illuminates the surrounding space uniformly. In a first embodiment the sack, which is made of at least partially light-transmitting material, comprises a transparent light-entrance orifice by way of which it can be attached to a light-exit orifice of the spotlight. The light-entrance orifice of the inflatable sack is preferably defined by a transparent foil connected around its circumferential edge, in an airtight manner, to the edge of a corresponding opening in the sack.
When the sack is closed on all sides in an airtight manner, it must be provided with a valve through which the sack can be inflated or, after use, can be deflated.
A second embodiment is characterized in that the sack is open at its light-entrance side, so that it can be inflated through the relevant opening by means of an external blower, which is preferably associated with the spotlight.
Particular mention should be made of the construction of the xe2x80x9clight sackxe2x80x9d, which is such that in the inflated state it has substantially the shape of a cylindrical rod, a sphere, a hemisphere, a cone or a truncated cone. When it is constructed in the shape of a cylinder its length can be from 1 to 10 m. The diameter is approximately 0.30 to 0.60 m.
Preferably the material of which the sack is made is air-permeable plastic film, which can be reinforced with textile.
It is also advantageous for the interior of the sack to be provided at least partially, in particular at its end face, with a light-reflecting zone, so as to produce a kind of luminous rod from which a soft light emerges radially.
Finally, it is of special significance for the blower used to inflate the sack, in particular the air outlet of the blower which opens into the sack, to be provided with a nonreturn valve, in particular a valve in which elastic tension is exerted in the closing direction, so as to prevent the escape of air from the sack after the blower has been turned off. This embodiment is particularly important when original-sound recording is intended.
Regarding the material for the xe2x80x9clight sackxe2x80x9d it should also be mentioned that sailcloth, in particular spinnaker cloth is suitable, because it provides both the desired light transmittance and the required stability. This material is not absolutely impermeable to air. Therefore when it is used, care should be taken to keep the blower continually in pressure-dependent operation, or to reactivate it whenever the pressure inside the sack falls below a predetermined level. However, as stated above, material that is not permeable to air is particularly suitable for the xe2x80x9cair sackxe2x80x9d, preferably textile-reinforced plastic film.
The terms xe2x80x9cairtightxe2x80x9d and xe2x80x9cimpermeable to airxe2x80x9d should be understood to refer to a material with a property such that a sack of which it is made can be inflated and will then remain in the inflated state for a certain period of time, in particular ca. 15-60 minutes, with no further addition of air or another gasxe2x80x94that is, for example, after a blower has been turned off. This feature makes the lighting device in accordance with the invention particularly suitable for original-soundtrack cinematography. Filmed speech sequences last on average max. 2-5 minutes, and to avoid background noises during this time the blower should be turned off. This is possible with the material just described, as soon as a predetermined air pressure has built up in the sack. The air pressure in the sack and thus the state of inflation of the sack are preferably monitored by a pressure sensor disposed inside the sack or on its outer surface.
The light transmittance or transparency of the light-sack material can vary, depending on the intended use; in particular, it depends on the degree and/or the nature of the tinting of the material. Preferably the light-sack material is extremely transparent.
The transparency should be as uniform as possible over the entire surface of the light sack; that is, preferably the light sack is coloured white approximately uniformly over its entire surface. However, it can also be provided with various patterns and/or colours in order to achieve special lighting effects. This can be advantageous primarily when one or more light sacks are themselves intended to serve as decoration, for instance when they form part of a stage set.
As mentioned above, in order to inflate the sack to a predetermined shape a blower device is provided, connected to the spotlight and/or to a sack-holding apparatus and/or is at least partially integrated therewith. The spotlight or a connecting element between spotlight and light sack, which is advantageously constructed as a sack-holding apparatus, can for example comprise inlet and outlet openings and associated tubes that can be connected to a blower in order to conduct an airstream for inflating the sack.
The means for connecting spotlight and sack in one preferred embodiment is a sack-holding apparatus connected to the spotlight and/or integrated therein, with which spotlight and sack can be connected. The holding apparatus is preferably detachably connected to the spotlight; however, it can also be an integral component of the spotlight. The holding apparatus comprises input and output tubes that can be connected to a blower in order to inflate the sack.
The holding apparatus can be connected to the spotlight by detachable devices, e.g. a snap closure, (rotatable) catch closure, screw threading or the like. If the means for attaching the light sack is integrated into the spotlight, it can take the form for example of a ridge running around the outer circumference of the spotlight parallel to its edge and set somewhat back therefrom, over which the light sack is pulled and behind which a band is positioned to hold the light sack in place.